Basically, you pay less when you buy in bulk. It's like you get a discount or offered a lesser price for the items because you bought a lot in number. Therefore, the consumer pays less per item. Once a consumer reaches a certain quantity of items, there is an introduced wholesale price which is a unit price lesser than usual which is already a big help to consumers.
Ironically, buying a lot at a time is cheaper than buying bit by bit. Places like Sam's Club specialise in having bulk supplies. People might not be planning to buy bulk, but after seeing how cheap it is, they'll decide to buy more than they planned. It creates the illusion of saving money to the consumer, but in reality, they spent more just because they liked the idea of getting more product. Hope that made since! :D
